[urq] 84 urq compression testing

[Justin]

Todd, couple things. It's important to hold the throttle body open, and do
the compression test when the engine is hot: reasons: hot piston rings tend
to expand when hot...effecting the compression...and a closed throttle body
will not allow the pistons to suck in enough air for a accurate compression
reading.

Grounding the coil wire will prevent the spark plugs from firing...a better
way, would just be to remove the two wires that supply the coil...(#1 wire
and #15...), that way the coil does not fire at all when cranking the
engine...(and no potential for sparks anywhere...).

Hold open the throttle body anyway you can...vice grips, screwdriver....etc.

When getting a compression reading, crank the engine until the gauge on the
pressure tester does not move anymore....(your looking for the maximum
compression each piston is able to produce...)

If it smells like it's running rich....defiantly investigate this....running
an engine excessively rich can cause premature wear, and possible detonation
on turbo engines...

Check the O2 sensor duty cycle, according to Bently....

Hope this helps...

Justin

(By the way, I had a shop once tell me my compression was low and needed to
re-build...found out on my own and from another shop that they were
wrong....be wary of this....)

----- Original Message -----
From: "todd ward" <ltw0808 at yahoo.com>
To: <urq at audifans.com>
Sent: Thursday, April 22, 2004 6:08 PM
Subject: [urq] 84 urq compression testing


> Just checking procedures for compression testing my 84
> urq. Bentley says to remove all plugs after car
> reaches normal operating temp. Then disconnect hot
> wire at distributor cap and ground it out with a
> clamp. Open the throttle. Nominal pressure 102-131 psi
> Minimum of 73 psi with a max difference of 29 psi.
> Question: where should I ground the igntn wire? And
> how should I hold the throttle open? Should only need
> 4-5 cranks until gauge will not rise any further
> right? My car would not pass emission so I took it to
> a shop where they did a compression and leak down
> test. It showed low compression and leakage of 70% in
> cylinder #1 and 85% in the rest. But the car seems to
> run fine. Its got a boost controller and probably some
> other mods I don't know about yet and smells like its
> running rich. But I just took it on a 600 mile trip
> and got 20-21 mpg running 80 most of the way. And the
> car has less than 80k on it. I don't think the shop
> would lie but it runs to smoothly for me to think it
> needs a 2-4k top end rebuild. No cutting out and pulls
> very well in high rpm 4-5k range. What would leakage
> like this show up as in every day driving? I was
> thinking the failure had come from a bad O2 sensor and
> maybe the mods dumping in too much fuel not bad
> valves. Know anybody in St. Louis? Thanks Todd
>
>
>
>
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